linux-kernel - Re: [PATCH v3 09/39] kasan: define KASAN_GRANULE

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Date:   Thu, 1 Oct 2020 19:33:26 +0200
From:   elver@...gle.com
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        kasan-dev@...glegroups.com,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 09/39] kasan: define KASAN_GRANULE_PAGE

On Fri, Sep 25, 2020 at 12:50AM +0200, Andrey Konovalov wrote:
> Define KASAN_GRANULE_PAGE as (KASAN_GRANULE_SIZE << PAGE_SHIFT), which is
> the same as (KASAN_GRANULE_SIZE * PAGE_SIZE), and use it across KASAN code
> to simplify it.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>

Reviewed-by: Marco Elver <elver@...gle.com>

> ---
> Change-Id: I0b627b24187d06c8b9bb2f1d04d94b3d06945e73
> ---
>  mm/kasan/init.c   | 10 ++++------
>  mm/kasan/kasan.h  |  1 +
>  mm/kasan/shadow.c | 16 +++++++---------
>  3 files changed, 12 insertions(+), 15 deletions(-)
> 
> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
> index 1a71eaa8c5f9..26b2663b3a42 100644
> --- a/mm/kasan/init.c
> +++ b/mm/kasan/init.c
> @@ -441,9 +441,8 @@ void kasan_remove_zero_shadow(void *start, unsigned long size)
>  	addr = (unsigned long)kasan_mem_to_shadow(start);
>  	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
>  
> -	if (WARN_ON((unsigned long)start %
> -			(KASAN_GRANULE_SIZE * PAGE_SIZE)) ||
> -	    WARN_ON(size % (KASAN_GRANULE_SIZE * PAGE_SIZE)))
> +	if (WARN_ON((unsigned long)start % KASAN_GRANULE_PAGE) ||
> +	    WARN_ON(size % KASAN_GRANULE_PAGE))
>  		return;
>  
>  	for (; addr < end; addr = next) {
> @@ -476,9 +475,8 @@ int kasan_add_zero_shadow(void *start, unsigned long size)
>  	shadow_start = kasan_mem_to_shadow(start);
>  	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
>  
> -	if (WARN_ON((unsigned long)start %
> -			(KASAN_GRANULE_SIZE * PAGE_SIZE)) ||
> -	    WARN_ON(size % (KASAN_GRANULE_SIZE * PAGE_SIZE)))
> +	if (WARN_ON((unsigned long)start % KASAN_GRANULE_PAGE) ||
> +	    WARN_ON(size % KASAN_GRANULE_PAGE))
>  		return -EINVAL;
>  
>  	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index c31e2c739301..1865bb92d47a 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -7,6 +7,7 @@
>  
>  #define KASAN_GRANULE_SIZE	(1UL << KASAN_SHADOW_SCALE_SHIFT)
>  #define KASAN_GRANULE_MASK	(KASAN_GRANULE_SIZE - 1)
> +#define KASAN_GRANULE_PAGE	(KASAN_GRANULE_SIZE << PAGE_SHIFT)
>  
>  #define KASAN_TAG_KERNEL	0xFF /* native kernel pointers tag */
>  #define KASAN_TAG_INVALID	0xFE /* inaccessible memory tag */
> diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
> index ca0cc4c31454..1fadd4930d54 100644
> --- a/mm/kasan/shadow.c
> +++ b/mm/kasan/shadow.c
> @@ -161,7 +161,7 @@ static int __meminit kasan_mem_notifier(struct notifier_block *nb,
>  	shadow_end = shadow_start + shadow_size;
>  
>  	if (WARN_ON(mem_data->nr_pages % KASAN_GRANULE_SIZE) ||
> -		WARN_ON(start_kaddr % (KASAN_GRANULE_SIZE << PAGE_SHIFT)))
> +		WARN_ON(start_kaddr % KASAN_GRANULE_PAGE))
>  		return NOTIFY_BAD;
>  
>  	switch (action) {
> @@ -432,22 +432,20 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
>  	unsigned long region_start, region_end;
>  	unsigned long size;
>  
> -	region_start = ALIGN(start, PAGE_SIZE * KASAN_GRANULE_SIZE);
> -	region_end = ALIGN_DOWN(end, PAGE_SIZE * KASAN_GRANULE_SIZE);
> +	region_start = ALIGN(start, KASAN_GRANULE_PAGE);
> +	region_end = ALIGN_DOWN(end, KASAN_GRANULE_PAGE);
>  
> -	free_region_start = ALIGN(free_region_start,
> -				  PAGE_SIZE * KASAN_GRANULE_SIZE);
> +	free_region_start = ALIGN(free_region_start, KASAN_GRANULE_PAGE);
>  
>  	if (start != region_start &&
>  	    free_region_start < region_start)
> -		region_start -= PAGE_SIZE * KASAN_GRANULE_SIZE;
> +		region_start -= KASAN_GRANULE_PAGE;
>  
> -	free_region_end = ALIGN_DOWN(free_region_end,
> -				     PAGE_SIZE * KASAN_GRANULE_SIZE);
> +	free_region_end = ALIGN_DOWN(free_region_end, KASAN_GRANULE_PAGE);
>  
>  	if (end != region_end &&
>  	    free_region_end > region_end)
> -		region_end += PAGE_SIZE * KASAN_GRANULE_SIZE;
> +		region_end += KASAN_GRANULE_PAGE;
>  
>  	shadow_start = kasan_mem_to_shadow((void *)region_start);
>  	shadow_end = kasan_mem_to_shadow((void *)region_end);
> -- 
> 2.28.0.681.g6f77f65b4e-goog
>